A rapid change is occurring in the commercial and industrial printing marketplace with an expanded use of digital printing presses to replace their analog counterparts. Digital printing presses have an advantage of lower “set-up” costs in that a change to a print pattern is accomplished with a file change. This improves the economics of “short run” printing and reducing a need to print large inventories of a given design.
One common form of digital printing press is a web press based upon inkjet printing of radiation curable inks. In this embodiment a roll of media is unwound and then passed through a paper path defined by a series of rollers. A part of the paper path is a print zone within which inkjet printheads eject a dot matrix pattern of fluid drops on a surface of the media thereby forming images and/or text on the media surface.
An important factor with radiation curable inks is a tendency to flow between depositing the inks and providing a radiation cure of the inks. Another factor is a tendency of inks having different primary colors to intermix. A certain amount of flow and intermixing can be desirable but there is an optimal level in order to maximize resultant image quality.
To control flow and intermixing PIN units can be used to “pin down” the ink to a certain extent to reduce flow and mixing. The effect of these units has been found to change with the transport speed of the print unit in unexpected ways.
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.